Caulking guns are used to dispense a wide variety of fluid compositions such as urethane, vinyl, polyester, epoxy and other plastics. These compositions are often very dense, yet the caulking gun must be capable of applying the composition over a wide range of volumetric flow rates. In order to achieve higher flow rates, prior art caulking guns were necessarily small in size. Otherwise, the force required to operate the caulking gun would exceed the capabilities of the operator. Consequently, complex gear-drives and pneumatic caulking guns were developed to overcome the problem. However, these improved caulking guns share a common characteristic. They are very expensive to manufacture and produce. There is a clear demand for an inexpensive hand-held caulking gun capable of delivering a dense composition at a high delivery volume and flow rate. U.S. Pat. No. 4,081,112 issued to Chang addresses the demand. The Chang caulking gun positions the trigger pivot and trigger drive grip engagement above the plunger shaft. This improvement increases the leverage obtainable by a hand operated trigger and allows delivery of the composition at a higher volume and flow rate than was previously possible in a hand-held caulking gun. Moreover, the improvement can be accomplished at no additional cost.
Nevertheless, there is an ever increasing demand for a hand-operated caulking gun having more power and improved features.